Current construction practice for interior and some exterior (such as soffits) surfaces relies primarily on gypsum board (drywall). Gypsum is a mineral found in nature as calcium sulfate dihydrate. Crushed and ground powder of calcined gypsum (calcium sulfate hemihydrate) is mixed with water and additives to form a slurry. This slurry is fed between two layers of paper and allowed to dry/harden, to make conventional gypsum boards. This simplistic system has served the construction industry for decades. However, it suffers several disadvantages that the present invention addresses. First, noise reduction performance is poor. A typical gypsum wall shows an NRC (noise reduction coefficient) in the range of 0.01 to 0.04. In contrast, acoustical tiles have an NRC on the order of 0.45 to 0.85. Second, standard gypsum boards exhibit poor thermal insulation. A xc2xd-inch board has a heat transfer resistance (in metric units) of 0.45. In contrast, a 1-inch fiberglass insulation of polystyrene foam shows a resistance number on the order of 4. Further, gypsum boards are heavy. Finally, when scribed and broken, loose powders create mess and potential health hazards.
This application discloses a class of materials for making wallboards and other related elements for residential and commercial construction. More particularly, the present invention discloses a systematic method of microstructure engineering, designed to create construction materials of controlled morphology and superior sound isolation and thermal insulation properties. A key and distinguishing feature of such materials is that they possess specially engineered microstructures comprising both inorganic and organic components. Another main characteristic is controlled morphology, ensuring microscopic voids dispersed throughout the system. Resilient polymeric binders with viscoelastic damping properties cover microscopic inorganic particles, forming a crosslinked, percolating network. The inorganic kernels of the coated particles provide mechanical and dimensional stability as well as fire/flame retardancy. The viscoelastic polymer network contributes cohesion and sound attenuation. Finally, the air phase may form either a co-continuous, tortuous phase, intertwining the particular network throughout the system, or simply exist as a collection of dispersed voids. In either case, thermal insulation afforded by this new board structure is greatly enhanced. In addition, the numerous interfaces created by blending the inorganic and organic components in contact with the void phase result in impedance mismatch of vibration transmission and a large number of destructive interferences of transmitted/reflected waves; both phenomena cause sound attenuation. Therefore, this approach to controlled microstructural engineering for construction materials yields improved acoustical properties over conventional wallboards. The novel construction materials disclosed herein exhibit significantly lower density than conventional materials, facilitating their installation. A consequence of the heterogeneous, textured morphology is the lowered density and weight savings. Yet another desired outcome is the improved workability of the resulting wallboards. Finally, the engineered materials may be filled between any two surfaces, such as wood veneers, to make lightweight doors. Alternatively, when overcoated with a scratch-resistant surface layer, lightweight countertops can be made.